1. Field of the Invention.
This invention relates generally to a downhole motor connected near the end of a drill string to drive a drill bit for forming borehole during the drilling for oil and gas and, more particularly, to a quick release coupling for the drive shaft of such a motor.
2. Description of the Prior Art.
Downhole motors are well known in the art of drilling for gas and oil and are particularly useful in situations such as directional drilling where it is preferred that the drill string is maintained stationary while the bit rotates. The motor is confined within a tubular housing, containing the rotor and stator thereof, threadably connected to another tubular portion of the housing enclosing the thrust bearing and radial bearing sections which support the rotating part through an interconnecting drive means therebetween. Due to the limited size of the borehole, the motor housings seldom exceed twelve inches in diameter and usually are on the order of six to eight inches. The limited diameters confine the internal design of the motor and bearing components causing the motor to be axially elongated in order to have a motor with sufficient power to rotate the drill bit. Because of the axial length, it is normally necessary to have threaded joints in the motor housing in addition to having joints in the interconnecting drive shaft assemblies to facilitate manufacturing and repair and maintenance at the rig site.
For ease of assembly it is desirable that the drive shaft within the housing be quick coupled, or have slide connections to facilitate handling and assembly by unskilled labor. Examples of such type of connections are well known in the art as shown for example in U.S. Pat. Nos. 2,990,895 and 3,159,222. While such connections as described therein have the ability to be quickly assembled and disassembled, vibration in the drive train will cause chattering resulting in excessive wear of the connector, ultimately resulting in failure thereof requiring premature tripping of the string to replace or repair the motor.